Abstract
Introduction: Bone loss following hip replacement is common. Its role in prosthesis stability and survival is a concern. DXA allows the assessment of adaptive bone remodelling and resorption. We prospectively examined longitudinal bone density changes affecting the Elite Plus [DePuy International Ltd], Leeds, UK), the Ultima Straight Stem (USS) [DePuy], the Exeter [Stryker Howmedica International Ltd, London, UK] and the Ultima Tapered Polished Stem (TPS) [DePuy] to determine whether bone loss was design dependent.
Methods: 164 patients were randomised to one of 4 stem designs. Patients received DXA peri-prosthetic examinations using the LUNAR EXPERT-XL at 7 days, then at
6, 12, 18 and 24 months. Custom analysis software was used to improve precision. Zones were excluded if identified as affected by heterotopic ossification post surgery. For each group the mean and standard error was determined for each follow up. 137 had follow up data to 24 months.
Results: Considering the whole peri-prosthetic region, all stems lost 5–9% BMD in the first 6 Months. The USS lost the most bone and the tapered stems, the Exeter and the TPS the least. Over the next 18 months changes were no more than 2%. The greatest losses were in the proximal zones, ranging between 8 and 20%. The USS lost significantly more (p < 0.05) than the others at 24 months. In zone 5 the TPS exhibited significantly higher recovery than the other designs at 24 months.
Discussion: Whilst the bone remodelling of the two tapered designs was largely equivalent, they exhibited a significant difference in the distal medial region. This study shows evidence that non-subsiding stems lose more bone than tapered subsiding designs.
Correspondence should be addressed to The Secretary, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
